Many applications require large quantities of earthen material to be moved from one location to another. Primary examples include removing overburden in a mining operation, or removing coal from a coal mine in an open cast or pit mine. Post-mining reclamation efforts also require large quantities of earthen material to be moved, primarily replacement of overburden in open cast mining operations and topsoil on top of the replaced overburden. Other examples of large scale earth moving operations include sand and gravel mining, as well as moving large quantities of earth to fill marshy areas and the like for future development or farming efforts.
Examples of equipment which have been used in the past for large earth moving operations, particularly open cast mining operations, include the drag line which is popular in open pit mining in the United States. Other types of known apparatus include the bucket wheel excavator which has a large rotating wheel extended at the end of a boom, wherein the wheel has a plurality of buckets disposed on its outer periphery which remove earth from the face of an open pit mine and deposit it onto a conveyor belt. In bucket wheel excavators, the boom supporting the bucket wheel may move from side to side or in a generally vertical direction. Bucket wheel excavators are among the largest machines known to man. As would be expected, the price for such machines is proportional to the size of the machine.
Yet another example of prior art large scale earth moving equipment includes the shovel. Large shovels may extract significant volumes of earthen material in a single pass. However, ancillary equipment must be used in conjunction with the shovel to handle the single slug of earthen material which is discharged from the shovel. Such ancillary equipment may include hoppers for metering the material onto a conveyor belt or large dump trucks for moving the material from the excavation site to a processing site. Use of shovels results in an inherently discontinuous process and also requires expensive ancillary equipment such as the dump trucks and auxiliary hoppers and conveyors.
In such large scale earth moving operations, the earthen material must frequently be moved over large distances. Typically, this is accomplished by overland conveyors which may be a mile or more in length. Notwithstanding their long length, the overland conveyors are designed in segments, with each segment engineered to sustain the peak load anticipated on the conveyor belt spanning that particular section. The more weight which is anticipated to be carried by any given particular section of the overland conveyor, the more robust the conveyor will need to be, and consequently the more expensive will be the cost of building and maintaining the conveyor. When, in the earth moving operation, the earth is deposited on the overland conveyor in discontinuous or discrete quantities, peak loads will occur on the conveyor. The conveyor must therefore be designed to sustain the peak load, rather than the average load. It is therefore desirable to eliminate the peaks and provide a more continuous flow of material on the overland conveyor and thereby reduce the design requirements, and concomitantly the cost, of the conveyor.
Even bucket wheel excavators do not result in a truly continuous or even load of earthen material on conveyors. Solutions are to install a hopper system at the head of the overland conveyor and thereby distribute the material on the conveyor in an even manner. However, this adds additional cost to the earth moving operation.
Even when a hopper is provided at the head of the overland conveyor, in most operations an intermediate conveyor must be provided between the earth removing equipment and the hopper. Such intermediate conveyors may be several hundred feet or more in length, and it is therefore desirable, if possible, to reduce the load requirements for these intermediate conveyors as well.
What is therefore needed in the art is an earth removing machine which is inexpensive to purchase, operate and maintain, is relatively flexible in facilitating movement of the equipment from one location to another, and which provides a continuous flow of material to an overland conveyor system.